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Title: Microwave radiation control using textured surface substrates
Author: Simms, Stephen William
ISNI:       0000 0001 3412 144X
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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The main objective of this work was to study the behaviour of antennas constructed using textured surface substrates, and to a certain extent provide control over their farfield radiation patterns. The properties of the textured surface have been analysed in terms of numerical electromagnetic simulation and by measurement, revealing both artificial magnetic conductor and electromagnetic bandgap properties. It is shown through measurement that by engineering the reflection phase response of such surfaces they can be made to reflect an incident circularly polarised .wave with the same sense as that of the incident polarisation, or with a sense opposite to that of the incident wave. Such properties can be potentially useful in radar cross-section control. Having characterised the textured surface, we then demonstrate its use as an efficient ground plane for a wire dipole. For this structure, we demonstrate that the dipole excites surface currents which, in turn, contribute to the far-field radiation pattern. This is confirmed by the examination of the 'measured near-field and far-field energy distributions close to the antenna. By introducing surface anisotropy to the structure, we further demonstrate far-field radiation pattern control. A novel method of feeding such structures was proposed, using a slot etched in the ground plane, in order to provide excitation to the antenna. Further, we show that careful placement of surface mounted resistors connecting adjacent patches can influence the confinement of surface currents, and as a result produce a more directive radiation pattern. We also show that by selectively interconnecting textured elements, the current distribution can be modified such that we can switch the far-field pattern from sum to difference mode.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available